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Batteries/Saftey/Lithium 060710
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(July 2006) Hewlett-Packard (HP) recalls digital cameras due to fire hazard.
About 224,000 units in the U.S. (about 679,000 worldwide) are involved. The digital camera can cause certain non-rechargeable batteries, such as the Duracell CP-1, to overheat when the camera is connected to an AC adapter or docking station, posing a fire hazard. HP has one report of a camera catching fire, damaging the camera and its docking station and causing minor smoke damage to the room. The recall involves the HP Photosmart R707 model. Consumers should stop using the recalled cameras and contact HP as they have developed a firmware update that prevents the camera from applying a charge to a non-rechargeable battery. Consumers are asked to not use single-use, non-rechargeable batteries until the firmware has been updated.
Meanwhile, other safety incidents have been reported which are not related to official recalls.
• Dell is investigating an exploding laptop which caught fire while it was on a table at a conference in Japan in late June 2006. The Inquirer technology website posted pictures of the resulting flames from the computer.
• Three publications, The Mac Observer (06/15/06) and The Sydney Morning Herald (06/22/06) and Mobile Magazine (05/04/06), have articles on the Lithium polymer batteries in MacBook Pro computers that are not working well. Some of the batteries are reported to be “swelling.” Swollen batteries pose a potential fire hazard and should not be used. Apple is replacing batteries which seem to have a fault or do not exhibit “normal operating behavior.”
• Eaton Corporation is also recalling batteries in their E1XM-Model AM/FM/SW/XM radios with serial numbers 3,067 - 5,642. The battery can overheat when using the AC adaptor.
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From Power Sources 2006...
Power Sources for the Military
The Safety of Lithium-based Chemistry Gets Primary Attention
by Shirley Georgi
Noting the increased growth of Lithium-based cells as the best answer for high-performance batteries for both commercial and military applications but yet understanding the crucial need to enhance this chemistry’s safety, the conference committee chose to provide three sessions on Battery Safety/Quality at Power Sources 2006. This is an increase of one total session, providing a time parameter for the largest number of papers ever presented at this conference specifically addressing the safety issue.
Recognizing the Need
In mid-June 2006, the NTSB (National Transportation Safety Board) announced that it will convene a two day hearing on July 12 -13th to consider safety issues surrounding cargo aircraft and potential risks of transporting lithium batteries. Part of the agenda will include:
- the design, testing and recalls of lithium batteries
- regulations concerning shipping lithium
- aircraft fire detection and suppression systems.
The hearing is part of the board’s ongoing investigation into the fire on-board a United Parcel Service (UPS) DC-8 on February 8, 2006 ; the plane, which was severly damaged, landed at the Philadelphia International Airport. At the present time, transporting lithium metal on a passenger aircraft is prohbited but on cargo aircraft, it may be shipped if each individual package weighs less than 15 kilograms, according to NTSB regulations.
Nearly a month goes by when there is not a U.S. Consumer Products Safety Commission (CPSC) recall associated with a battery, the majority having Lithium-ion chemistry. In 2005, there were over 50 incidents or injuries from fire or explosion in laptop and cell phone batteries, according the CPSC. At the Power Sources Conference, Brain Barnett of TIAX noted that localized temperatures in some of these cells must have exceeded 6000C, based on information from news reports. Although safety incidents being reported are at a failure rate one in a million (or possibly less), the battery industry needs to take a serious look at what Dr. Barnett calls “field failures.”
Field failures are not predictable and are not considered in the same category as “predictable abuse tolerance failures.” The field failures are difficult to evaluate at the cell level or through quality control. To gain understanding into the problem, it is critical that materials in the batteries be evaluated for relative kinetics and pressures. Dr. Barnett noted, “To minimize the damage that can be caused during a failure event initiated by an internal short, it is important to understand and control the kinetics of heat release and gas generation from decomposition of the active materials during such a simulated thermal event.” Based on examining field failures, the PTC (Positive Temperature Coefficient) , (CID Current Interrupter Device), shutdown separators and electronic controls were not effective in those cases.
The Response
¨ TIAX has expertise and experience in examining “field failures.” Although Differential Scanning Calorimetry (DSC) and Accelerated Rate Calimetry (ARC) tests have been very valuable in examining material safety properties of cells, Dr. Barnett notes that “conventional material safety testing methods must be modified or augmented with additional information in order to determine the relationship between material properties and the heat release kinetics.” Currently, TIAX is developing instrumentation to measure the heat release at higher scan rates. (Session 3.2)
Pouch cells - positive results
¨ Joon Kim, CEO of Kokam America, Inc,. opened the conference by explaining the safety aspects of the company’s patented folder-to-folder cell assembly technology. This assembly process allows flexibility of cell design in terms of rate capability and cell capacity. Their superior lithium polymer batteries (SLPB) have high rate (up to 20C rate) and large capacity (up to 240Ah). “The enhanced safety and lower Ohmic resistance are believed to be due to the stacked type of cell structure applied in the SLBP cells,” Dr. Kim noted. He emphasized that overcharge protection is the most important issue in field applications of large capacity cells. He stressed that in their stacked type design in a soft pouch pack the “initial gas generated under overcharge condition can be released through cell seal area of soft pouch pack before it reaches critical conditions.” (Session 1.1)
¨ Judy Jeevarajan of NASA-Johnson Space Center reviewed her tests of a new Lithium-ion 4.0 Ah pouch cell with a traditional liquid Lithium-ion cell electrolyte from GS Yuasa. All tests showed that the cells did exhibit any electrolyte leakage, venting or fire. (Session 1.2)
¨ The high-power 9 Ah HP-0411700260 pouch cell produced by Lithium Technologies GAIA was also tested for performance and safety at the NASA -Johnson Space Center. This cell can operate with a maximum charge current of 8 A and a maximum discharge current of 72 A. The cell performed well in the short circuit test and delivered at least 967 W/kg instantaneous power. The cell was also tolerant to overcharge and overdischarge at 1.8 A, venting without fire or smoke.
(Session 1.3)
¨ Quallion, working with the US Army - CERDEC (Communications, Electronics Research, Develpment and Engineering Center) , developed a new primary BB2590 battery pack with 22% improved capacity and bullet-shot safety. CERDEC-Quallion cells were tested and compared with commercially available 4 Ah LiCoO2 pouch cells; results showed that only the CERDEC-Quallion pack did not catch fire in the bullet-shot test. (Session 1.4)
The cell - the role of its components in thermal runaway
¨ The Advanced Power Sources R &D Department at Sandia National Laboratories has been working on the role of separator in overcharge response of 18650 cells. Based on their testing, the breakdown response of the separator is believed to result from electrical breakdown of the separator material itself. For example, Celgard Trilayer separator has stability in its polypropylene components up to its melt temperature (1550 C). Their results indicate that separator breakdown likely “results from a pin hole that forms some time after shutdown and eventually propagates to a hard short under the high applied potential.” New separator materials, with different shutdown properties and without shutdown properties, are being evaluated. (Session 3.1)
¨ Policell, Technologies Inc. has developed a large format Lithium-ion cell with improved safety, by utilizing its bondable (or heat-activated) separator and its advanced electrolytes. The bondable separator has a shut-down temperature of 1100 C which is much lower in comparison to two other popular commercial separators. Policell’s electrolyte has an extended temperature range for battery applications. Policell notes that using the new separator and electrolyte in Lithium-ion cells results in:
- better performance (including low and stable impedance, high rate capability , longer cycle life and higher energy density)
- lower thermal shut-down temperature
- a wider temperature range
- improved safety
(Session 3.3)
¨The U.S. Army RDECOM (Research, Development and Engineering Command) is collecting data on the changes in kinetic behavior of Lithium-ion cells as they cycle. Data confirms that changes in kinetic behavior occur as Lithium-ion cells age. The data has provided valuable information for both improved charge routines and safety analysis. Research is continuing to fully understand the processes affecting the behavior of cycle aged cells; more studies are being done on their thermodynamic properties. (Session 3.4)
¨ U.S. Army RDECOM is also studying thermal considerations of electrically stressed batteries by using thermal imaging. Thermal imaging is being utilized to identify a problem with available army batteries (i.e., Lithium -ion batteries such as the BB-2590 the BB-2847) and the development of novel power sources. Gathering such information is invaluable since electrochemical systems are approaching or exceeding explosives in terms of energy density. Safety is an issue for both storage and usage. (Session 3.5)
Safety testing of batteries “in the field”
¨ In 1999, a battery containing 294 cells in 7 modules of 42 DD lithium/sulfur chloride cells in a 7S6P configuration exploded during pigging (pipeline inspecting) of a 30” gas pipeline. The pressure in the pipeline was ca 160 Bar. Testing was done by Forsvarets foskningshinstitutt, Norweign Defense Research Establishment, to determine the cause of the explosion. Testing involved exposure of lithium batteries to external hydrostatic pressure. One immediate result of the testing showed that base cells exposed to external pressure develop a leak in the top of the cell.
As a result of the testing, it was determined that potting of cell tops should not be done in batteries that may be exposed to external pressure. Sequential discharge of battery modules is recommended to increase safety. The author also noted that it is good practice to use a weak lid or safety valve on the battery container. High pressure battery containers should not have their lids bolted. (Session 5.1)
¨ The U.S. Navy NSWC (Naval Surface Warfare Center) Crane Division was asked to test 900mAh and 1500mAh cell phone batteries by the CPSC (Consumer Products Safety Commission). Tests were conducted in either open-air or in a containment vessel. This total test effort was designed to simulate consumer reported events occurring under charging of cell phone batteries. As a results of the tests, it was determined that the cell phone batteries do vent under overcharge and extreme heat conditions. Batteries expelled volatile organic compounds when venting due to abuse conditions. During an event caused by abuse conditions, temperature and pressure are severe enough to cause significant personal injuries. (Session 5.2)
¨ The U.S. Navy is increasingly using more Lithium-ion batteries. Two sizes which are being used more frequently are the D-size cells and the 18650 cell. These cells have been used in unmanned vehicles. The U.S. Naval Surface Warfare Center (Systems & Materials Power & Protection Branch) tested these cells. As a result of the testing, they have provided a list of recommended guidelines:
- Special consideration must be given to wire placement and potential electrical and environmental abuses. Batteries with many cells need redundant safeties from short circuit.
- Safety features internal to the battery must be present and active. These include overcharge, overdischarge and short circuit.
- If the battery is in a pressure vessel which can constrain high-temperature outgasssing, consideration needs to be taken to evaluate potential failure from propagation within the battery.
- Paper designs of electronics should be tested to confirm the operation these circuits, including those for normal operating procedures as well as abusive procedures.
(Session 5.3)
¨ The U.S. Navy NSWC Crane Division also analyzed gases evolved from vented Lithium-ion cells. These large capacity cells (51 Ah and 350 Ah) were subjected to abusive overcharge while contained in a known free volume. Specific sampling techniques were used to analyze organic components (i.e., hydrogen fluoride) evolved from these cells.
Important findings indicated that organic compounds released from a vented Lithium-ion cell are a hazard and can cause short and long term health problems. Under abuse conditions, levels of hydrogen fluoride from the vented cells are toxic. Gases stemming from an abused Lithium-ion cell should never be inhaled or absorbed into the skin because of the toxic effects of hydrogen fluoride.
Lithium-ion venting in an enclosed space results in multiple hazards. This can include fire, explosion and gassing.
During the testing, it was noted that the overcharge portion of the experiment indicated significant changes can result from minor changes in the abuse testing. Thus, characteristics of organic compounds released from the variation in events also changed. (Session 5.4)
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As Lithium-ion battery energy densities have continued to rise in an effort to keep pace with the ever increasing demand for portable power, a increasing vigilance for battery safety is required. To date, cell and battery companies have employed a series of safety mechanisms to address these concerns by offering a "Safety Threshold." Advances in Lithium-ion technology have exceeded this threshold, however, as evidenced by the ever increasing number of Lithium-ion battery failures. Quallion LLC's SaFE-LYTETM Technology offers a solution by raising the bar and creating a new, higher "Safety Threshold" that allows for great cell and battery safety. SaFE-LYTETM achieves this through introducing a fire suppressant additive into the cell where safety mechanisms are most needed, without compromising performance. Paul Beach ,V.P. Business Development, Quallion LLC. +
A Lithium-ion cell with safety devices. A: The disc is a temperature sensitive polymer that resists electron flow as the temperature increases. B: The CID opens with internal pressure breaking the cell circuit. C: Increased pressure causes the CID to vent to the cap. D: A polymer sheet between the anodic and cathodic foils melt at a given temperature, stopping the electron flow.
An example of a lithium battery pack after explosion or rupture. Credits: http://www.cdc.gov/niosh +